1. Field of the Invention
This invention is concerned with the processing of pile fabrics. More particularly, it relates to a method and apparatus for the treatment of pile fabrics using a plurality of controlled electrifier cylinders in tandem.
2. Description of the Prior Art
Within the content of the present invention, the general classification "pile fabrics", covers a variety of materials. These materials range from fine velours to heavy carpeting, and include such diverse products as napped liners, suedes, flocked prints, velvets, and double-sided blankets. The basic cloth from which such pile fabrics are produced may be knitted, tufted, or woven.
Pile fabric processing, irrespective of the particular material involved, is primarily concerned with developing a final product having desired characteristics and appearance. Usually, when this objective is achieved, the individual fibers of the product have a particular length, amount of tangle, and lay. Permanence of the finish is important.
A well recognized treatment for finishing pile fabrics employs rotating electrifier cylinders. Such elements consist of large heated metallic cylinders having a pattern of grooves on the surface. The heat of the cylinder serves to soften synthetic fibers and an electrostatic charge is imparted which assists in straightening and untangling each fiber. The surface grooves treat the fabric in a number of ways including: beating, rubbing, twisting, and erection.
As explained more fully hereinafter, a wide variety of surface groove patterns have been used to achieve optimum or special pile finishing effects. A recent development in this area is disclosed in U.S. Pat. No. 3,557,415 granted to D. Kloeckener in Jan. 26, 1971, The electrifier cylinder in this patent has a first plurality of grooves disposed with a relatively shallow pitch across the width of the cylinder and a second plurality of steeply pitched grooves disposed in intersecting relationship with the first plurality. As described therein, this configuration of grooves makes it possible to simultaneously effect longitudinal and cross-sweeping of the pile.
Although it has been well recognized that the depth of penetration of pile treatment, the permanence of the finish, and the lay of the pile are determined by such factors as the temperature of the cylinder, the degree of fabric wrap about the cylinder, the groove configuration and speed of cylinder rotation, the prior art has not provided a versatile method or apparatus for varying these critical conditions within a worthwhile range. Prior to the present invention, an operator was confined to using a particular cylinder with its specific groove configuration. The temperature of the cylinder could be varied to establish the slope of the linear temperature gradient experienced by the fabric during treatment; but the shape of this gradient could not be controlled. The groove power and its effect upon beating, oscillation, erection, and ultimate lay could be enhanced or decreased by changing cylinder speed; but the general characteristics imposed by the particular groove configuration, e.g. a right or left-handed lay, could not be modified.
Techniques for optimizing the available range of operation from a single electrifier unit are disclosed in U.S. Pat. Nos. 3,413,695, 3,465,397 and 3,586,228, granted to the inventor in Dec. 3, 1968, Sept. 9, 1969 and June 22, 1971, respectively; in each instance it will be appreciated that the operator was restricted by the limited range of temperature and groove power available with the specific electrifier cylinder employed. Since these cylinders are both large and expensive, one cannot easily stock a variety for interchange depending upon the fabric or fabric treatment contemplated.
In the past, the treatment of pile fabrics has often included multiple passages of the fabric through electrifier units. The number of passes depended upon the original set of the fibers and the desired final finish. In order to obtain greater changes from the original set, the processor was limited by the inherent design limitations of the cylinder employed. In 1960, Hart U.S. Pat. No. 2,961,733 disclosed the use of two electrifier cylinders upon a single unit, in order to expedite the processing of a fabric in a single passage. Necessarily, Hart was restricted to the use of existing cylinder designs. Thus, the Hart apparatus was able to produce in one passage the cumulative effect of two passages using single cylinder units.